The present invention relates to compact discs and related devices, such as CD-ROMs, laser discs and cleaning CD's, having a profile other than circular. In particular, the invention relates to processes for manufacturing this novel type of compact disc.
Presently, all compact discs have a circular profile shape. It is common that a label containing artwork or other visually readable material is applied to the upper, non-functional face of the compact disc. Since the normal compact disc is round, the label may be applied in any radial direction so long as the label is properly centered.
However, the orientation of a non-round compact disc changes about the perimeter of the disc, the label must be applied not only in centered fashion, but must also be aligned in the proper radial direction with respect to the disc perimeter or profile. It therefore becomes necessary to label and manufacture non-round compact discs to insure that the label is properly aligned in the desired orientation.
Is it currently considered to be a requirement that compact discs have a circular outer profile, based on the process by which information is read on the compact disc by a reading machine, such as a compact disc player. The disc rotates about a central axis in a receiving tray of the player with respect to a laser-based reading element, and therefore, the information on the disc must be arranged in a circular fashion. Since the disc must rotate within the player, it is of course most convenient to have the disc as a whole shaped with a circular outer profile, with the player shaped to receive the circular disc.
However, it has now been discovered that it is possible to provide a compact disc having a non-circular outer profile. FIG. 1 shows a heart shaped compact disc in bottom plan view, although any non-circular disc is within the scope of the invention. The radius r.sub.1, of such a non-round disc 2, measured from the center of the disc (i.e. the center of the center hole 10) to the furthest point 6 on the outer profile 8, should be sized to fit within the usually round receiving tray of an appropriate CD player. In other words, the radius r.sub.1 must be less than or equal to the inside diameter of the receiving tray. However, since the non-circular compact disc will have the usual center hole 10 found on standard round compact discs, these non-circular discs will also properly spin within the receiving tray of a CD player.
While the outer profile of the CD of the invention may be of non-round shape, the readable digital information 12 provided on the disc must be provided in the usual annular arrangement. However, in order to insure that all of the intended information will be readable, the outer limit 14 of the annularly arranged information region must not extend beyond the innermost point 16 of the outer profile 8.
Compact discs generally possess a so-called stacking ring about the center of the disc, which acts as a spacer to prevent damage to the disc surface when stacked with other discs. However, the spaces resulting between the stacked discs become problematic during a shaping process in which a plurality of stacked discs are simultaneously shaped. In particular, dust and other debris from the shaping process tends to enter the interstitial area between discs and could result in damage to the delicate disc surface.